Ooops, sorry, didnt read the blurb, i just saw the word cloud and thought it meant it was stored offsite.
tbh, your solution is really gonna depend on how much you want to spend and how much you expect your needs to grow, and how much the photos on the drive mean to you.
The WD box is fine as an external disk, but by the sounds of it, its only gonna introduce another single point of failure, so if the disk dies, you're stuffed (Clearly, if you're using it only as a backup for the content on your main internet drive, then that's perfect, just buy it and read no more).
Another option is to buy a synology or qnap nas box and then insert your own choice of enterprise NAS quality HDDs (which are typically more reliable than the consumer quality drives found in devices like the WD box.). I bought a 2-drive synology NAS for my brother, and a 2-drive qnap NAS for myself. The reason for buying the NAS was i wanted something that had more expansion capabilities and could also connect up to the TV to act as a media server. I havent listed the box names as they come out with new ones every year, so get the latest one that has enough space for your future needs. It's more expensive, but might be a better option than a single NAS drive, and in most cases (and depending on your config), you can buy the empty NAS box, add in one drive now and then add a second drive in the future (when cost/TB drops).
Personally, I store my can't-lose files and active files on my macbook and imac, and these are backed up to an apple time machine continually and to the NAS nightly (on drive 1). I also keep lots of other files (mostly archived videos and photos) on the NAS drive 2, and everything from everywhere is backed up weekly to amazon drive (which in itself stores the contents in three different data centres from what i remember). I'm also considering encrypting some of my backups to the cloud, so that no one could access the contents even if there was some massive botch by amazon.
You will have different needs, but hopefully this gives you a picture of one workflow that seems to work ok for me anyway. It'll be stupidly overkill for some, and crazily reckless for others (so if anyone is gonna tell me my config is JBOD rather than proper RAID, please get a life).
But i'd recommend not relying on a single drive if you can't live without the contents.
Lastly, i dunno how convinced i am about the WD personal cloud option though. Personally, I'd trust amazon or dropbox to maintain its servers secure, more than i'd trust myself to properly configure a personal cloud that gave access to my NAS to the entire internet, and which relied on WD to continue to maintain the software's integrity into the future.
(EDIT - i removed an external link to storagereview leaderboard as the article was out of date)
